Amir R, Devor M
Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
Neuroscience. 2000;95(1):189-95. doi: 10.1016/s0306-4522(99)00388-7.
Electrophysiological recordings were made in vitro from primary afferent neurons with unmyelinated axons (C-neurons) in excised rat dorsal root ganglia. Spike activity triggered in neurons with myelinated axons (A-neurons) by stimulation of the peripheral nerve or the dorsal root produced a transient depolarization in passive neighboring C-neurons that share the same ganglion. About 90% of neurons sampled responded with this "cross-depolarization". Cross-depolarization was associated with functional excitation as indicated by an increase in firing probability in response to previously subthreshold intracellular test pulses. Furthermore, it yielded a net increase of the input resistance of the affected C-neurons. We suggest that functional coupling among DRG neurons could serve a metabolic role, providing a functionally relevant feedback signal useful for controlling the excitability of nociceptive sensory endings. In addition, the results provide a novel mechanism whereby afferent nociceptors could be stimulated by activity in low-threshold mechanoreceptors, particularly in the event of nerve injury. Hence, the coupling between afferent A- and C-neurons in dorsal root ganglia provides a novel candidate mechanism for neuropathic pain.
在体外对切除的大鼠背根神经节中具有无髓轴突的初级传入神经元（C神经元）进行电生理记录。通过刺激外周神经或背根，在具有髓鞘轴突的神经元（A神经元）中引发的动作电位活动，在共享同一神经节的被动相邻C神经元中产生了短暂的去极化。约90%的采样神经元出现这种“交叉去极化”反应。如对先前阈下细胞内测试脉冲的反应中放电概率增加所示，交叉去极化与功能性兴奋相关。此外，它使受影响的C神经元的输入电阻净增加。我们认为，背根神经节神经元之间的功能耦合可能起到代谢作用，提供一个对控制伤害性感觉末梢兴奋性有用的功能相关反馈信号。此外，这些结果提供了一种新机制，通过该机制，低阈值机械感受器的活动可刺激传入伤害感受器，尤其是在神经损伤的情况下。因此，背根神经节中传入A神经元和C神经元之间的耦合为神经性疼痛提供了一种新的候选机制。
